The present invention relates to tailoring the shape of a magneto-resistive material, and more particularly to a design of the shape of the magneto-resistive material to obtain a new type of position sensitive sensor.
The position of a moving object is often determined by means of the readout from a resistive sensor, usually of potentiometer type, which is mechanically connected to the object to be monitored.
In order to reduce the wear and thereby crease e reliability, it is desirable to eliminate the sliding friction encountered in the standard resistive sensors. Non-contact methods using e.g. inductively coupled coils is currently being introduced as replacement for the potentiometer sensors. However, these are more complex and therefore more expensive.
In recent years novel types of magneto-resistive materials with much higher sensitivity to moderate changes in magnetic fields have been found. These new materials showing giant magneto-resistance (GMR) or colossal magneto-resistance (CMR) make possible new types of position sensors.
In a document U.S. Pat. No. 5,475,304 is disclosed a giant magneto-resistant sensor including at least one layered structure. The layered structure includes a ferromagnetic layer having a fixed magnetic state, a second, softer magnetic layer, and a metal layer interposed between and contacting these two layers. The sensor also includes one or more indexing magnets for inducing a domain wall, at a measured position, between regions of nonaligned magnetic fields in the softer magnetic layer. By measuring the resistance across the magneto-resistant sensor a displacement of one workpiece, carrying the sensor, will be measured relative to another workpiece carrying an inducing means.
Yet another document U.S. Pat. No. 5,627,466 discloses a position measuring device having a sensor, the output signal of which is a function of the distance between a graduation and a scanning unit. Magneto-resistive elements, which scan the graduation, are disposed in the active branch of a potentiometer circuit. The voltage over the active branch is taken as the distance-dependent signal and is used to control the amplitude of the position-dependent scanning signals generated by scanning the graduation.
However, there is still a demand for non-contact sensor devices for position measurement offering a sensitivity function adapted to the particular application.
The object of present invention is to disclose a device, which forms a position sensor for non-contact position measurement The device comprises a sensor magnet and a sensor body made of a magneto-resistive material, whereby the magneto-resistive material is formed into a body having two or three dimensional geometrical shape to achieve a desired sensitivity function. The desired sensitivity function then results from a variation in one or more of the sensor body dimensions.
According to the object of the present invention the sensor body presents in different embodiments shapes like a simple wedge, a double wedge, a circular tapered form or an arbitrary shape to obtain the desired sensitivity function.